Ahh, first person. I used to do that a lot. Sometimes I'd be writing and the story should be in the third person, and at the end I realise I'd written everything as "I" and I have to go back and change it all! But anyway, not sure the first person thing works for me - I just end up writing myself - I keep doing that!
This is where a combination of what is in effect a stream of my character's consciousness but punctuated etc and the present tense force the character out. I find it helps having characters wildly different to myself - a seventeen year old boy, two gay men ranging in age from seven to one hundred and fifty and two OAPs with a seven year old boy. I can't put myself in them lol